1. Field of the Invention
The present application relates to an image forming apparatus that prints an image on a preprinted sheet, a control method for the image forming apparatus, and a storage medium.
2. Description of the Related Art
In an image forming apparatus discussed in Japanese Patent Application Laid-Open No. 2000-185881, an image reading unit is mounted in a transfer-paper conveyance path routed from a sheet feeding unit to a sheet discharge unit, so that a document conveyance system and a transfer-paper conveyance system are in shared use.
In the image forming apparatus as described above, before printing by a printing unit on a document in the sheet feeding unit, the document in the sheet feeding unit is read by the reading unit to acquire image data of the document, and, subsequently, printing on the document in the sheet feeding can be performed.
On the other hand, in such image forming apparatuses, some apparatuses have a paper conveyance path or a printing unit that enables printing in an overlay manner on a document of which one side or two sides of the document were preprinted. As such use application, overwrite printing for printing in an overlay manner on a document in which a prescribed form was already printed, or back surface printing for printing on an unprinted surface of a document in which only one side was printed, is conceivable.
In the case of performing such print processing, a document of which one side or two sides were preprinted is placed in the sheet feeding unit before a user executes print processing, and the image forming apparatus receives a print job (print data) transmitted from an information processing apparatus such as a personal computer (PC), so that overwrite printing or back surface printing is executed.
However, when the user transmits a print job from the information processing apparatus, in a case where it is unknown what document is placed in the sheet feeding unit of an image forming apparatus at a transmission destination, printing may be performed in some cases on an unintended surface of the document. For example, when overwrite printing is performed on a document on which a prescribed form was already been printed, in a case where the document having the printed prescribed form is placed with the front surface facing down and the back surface facing up in the sheet feeding unit, or in a case where white paper is placed in the sheet feeding unit, print processing may be performed on a surface that does not have the printed prescribed form. Alternatively, when printing on an unprinted surface of a document of which only one side was preprinted is performed, in a case where the document of which only one side was preprinted is placed with the front surface facing down and the back surface facing up in the sheet feeding unit, or in a case where a document of which two sides were preprinted is placed in the sheet feeding unit, print processing may be performed on a surface that is not white paper. This may cause a print result unexpected by the user. In this case, the user may take a time and labor such as reversing the surface of the sheet and re-setting the sheet in the sheet feeding unit, and sheets may be wasted due to erroneous printing.